Typically, a data signal read from a fuse is input to a buffer circuit including an inverter, an output signal from the buffer circuit is fed back to a latch circuit coupled to an input terminal of the buffer circuit, and the output signal is latched by the latch circuit as discussed in, for example, Japanese Patent Application Laid-Open Publication No. 2000-082296 or Japanese Patent Application Laid-Open Publication No. 2004-246992.
For example, a fuse where a current path between terminals of the fuse is cut off due to electric stress caused by a current flowing through the terminals of the fuse is known. The electric stress caused by the current flowing through the terminals of the fuse generates Joule heat and a low resistance element in the current path passing through the terminals of the fuse melts to be cut off due to the Joule heat. The process is generally called a “fuse blowout.” The resistance value between the terminals of the fuse is low before the fuse blowout. When the fuse blowout occurs, the resistance value between the terminals of the fuse becomes high. The change in the resistance value is utilized to store data or information in the fuse.
Preferably, after the application of the electric stress, the low resistance element between the terminals of the fuse melts to be completely cut off and the terminals of the fuse are completely decoupled, that is, the resistance value between the terminals of the fuse is infinite. However, in practice, there may be a case where the terminals of the fuse are not completely decoupled. In such a case, the resistance value between the terminals of the fuse is high.
When the terminals of the fuse are coupled in the high resistance state, a current path is formed to pass from a power supply voltage to a ground potential through the latch circuit and the fuse, and a leakage current may continue to flow through the current path. As long as the power supply voltage is supplied, the leakage current may flow through the current path also after the data or information is read from the fuse. As a result of the leakage current, current consumption may increase.